1. Field of the Invention
The present invention relates to a fuel injection valve, of an electromagnetic type, for example, that is mainly utilized in a fuel supply system.
2. Description of the Related Art
In recent years, while the regulation on exhaust gas of a vehicle or the like has been tightened, it has been required to raise the combustion efficiency of an internal combustion engine. In general, the particle diameter (spray particle diameter) of fuel injected from a fuel injection valve and the angle (spray angle) of the liquid film of the injected fuel are in a tradeoff relationship as represented in FIG. 1; in order to reduce the spray particle diameter, it is required to enlarge the spray angle. In a fuel-injection internal combustion engine, a fuel injection valve injects a fuel toward an intake valve, and the fuel, which attaches to the intake valve and hence is gasified, is supplied to a combustion chamber. However, when the fuel is sprayed, part of the spray, situated at a position that is away from the center axis of the spray, attaches to the inner wall of an intake port; therefore, some of the fuel travels on the inner wall of the intake port, becomes a liquid film, and flows into the combustion chamber in a delayed manner, thereby hindering the combustion efficiency from being raised.
When in order to reduce the particle diameter of the fuel, the spray angle is made too large, the amount of spray that attaches to the inner wall of the intake port increases and hence there increases the fuel that travels on the inner wall of the intake port, becomes a liquid film, and flows into the combustion chamber in a delayed manner; therefore, the combustion efficiency decreases. Accordingly, in order to raise the combustion efficiency, it is required that both the directivity and the atomization of the spray are satisfied. In order to satisfy both the directivity and the atomization of the spray, various kinds of studies have already been carried out to date.
For example, in a conventional fuel injection valve disclosed in Patent Document 1, there is provided, in an injection hole plate, a protrusion portion that protrudes downstream in such a way as to be parallel to the valve-body front end portion, and the injection hole right above height, expressed by the distance in the valve seat axis direction between the center of the inlet of an injection hole disposed radially outside the protrusion portion and the valve-body front end portion, and the diameter of the injection hole are made to be in a predetermined relationship with each other, so that both the directivity and the atomization of the spray are satisfied. Moreover, in a conventional fuel injection valve disclosed in Patent Document 2, a concave is provided at the outlet of each injection hole in order to promote the mixture of the fuel and air, so that the atomization of the fuel is facilitated.
Furthermore, in a conventional fluid injection nozzle disclosed in Patent Document 3, an injection hole, provided in an injection hole plate, is disposed inside a virtual circle obtained when the extended line of the seat surface of a valve seat and the injection hole plate intersect each other, and the diameter of the injection hole and the vertical distance between the valve-body front end portion and the injection hole plate are made to be in a specific relationship with each other, so that the atomization is facilitated. Still moreover, in a conventional fluid injection nozzle disclosed in Patent Document 4, an injection hole is enlarged toward the fluid outlet with respect to the axis of the injection hole, so that a liquid film, sufficiently widened in the injection hole, can be obtained.